1. Field of the Invention
The present invention relates to a cutting apparatus for concrete or the like used to break or cut a road pavement surface or concrete surface, and more particularly to a cutting apparatus for concrete or the like that features a holding structure of a blade cover that is attached to prevent dust such as cutting chips from scattering, and recover the dust.
2. Description of the Related Art
Where a road pavement surface or concrete is cut with a concrete cutter which is one of cutting apparatuses for concrete or the like, dust such as cutting chips is generated. This dust should be recovered as industrial waste. Therefore, some of the conventional concrete cutters are known to have a blade cover that is connected to a dust collection deice and attached around the blade, thereby making it possible to prevent dust generated by the cutting operation from scattering and suck in and recover the dust with the dust collection device.
In a concrete cutter used for cutting a road pavement surface, the body frame is typically supported by wheels (front wheels and rear wheels) and the concrete cutter is configured so that the inclination angle of the body frame in the front-rear direction and the height of the body frame on the front side can be changed. As a result, the cutting depth of the blade attached to the front portion of the body frame can be adjusted.
More specifically, in a concrete cutter 51 shown in FIG. 8, a body frame 52 is supported by a front wheel 53 and a rear wheel 54, and a blade 55 is attached to a side of a front portion 52a of the body frame 52. The blade 55 is attached to a distal end (protrudes toward the side of the body frame 52) of a rotating shaft 56 supported horizontally in the left-right direction of the body frame 52, and the blade is supported in a state such that a portion with a span of about 140 to 150° on the lower side of the blade tip protrudes below a bottom surface 52b of the body frame 52. The blade is configured to receive drive power from a motor (gasoline engine or the like; not shown in the figure) that is carried on the body frame 52 and rotates at a high speed.
The front wheel 53 is pivotally supported on a distal end of a support arm 57, and the support arm 57 is supported in a state in which a proximal end portion 57a thereof can rotate about a horizontal axis at an intermediate position in the front-rear direction of the body frame 52. By operating a cutting depth adjusting handle (not shown in the figure), it is possible to rotate the distal end side of the support arm 57 from a position shown in FIG. 8(1) to a position shown in FIG. 8(3). As a result, the inclination angle in the front-rear direction of the body frame 52 with respect to a central axis of a shaft 54a of the rear wheel 54 as a base point and the height of the front portion 52a of the body frame 52 (height from a cutting object surface G to a bottom surface 52b in the front portion 52a) can be changed.
The following problem is encountered when a blade cover is attached to the concrete cutter 51, such as shown in FIG. 8, in which the cutting depth of the blade 55 is adjusted by changing the inclination angle of the body frame 52 in the front-rear direction.
When the air under the blade cover is to be sucked in with the dust collection device in order to recover the dust, the blade cover should be held at all times so that the lower edge of the blade cover is at a position close to the cutting object surface G, regardless of the cutting depth of the blade 55. For this reason, the blade cover should be attached to the body frame 52 so that the blade cover could be moved in the upon-down direction.
Accordingly, some of the conventional concrete cutters are configured such that a slide guide with a side edge extending in the vertical direction is attached to the body frame 52 and a bracket capable of sliding along both side edges of the slide guide is attached to the blade cover, thereby making it possible to move the blade cover in the up-down direction.
However, in the concrete cutter of such a type, where the tilting angle of the body frame 52 in the front-rear direction is changed to adjust the cutting depth, the tilting angles of both the body frame 52 and the blade cover change and therefore the lower edge of the blade cover cannot be held in the horizontal state (state in which the lower edge is parallel to the cutting object surface G) and a large gap can be formed between the blade cover and the cutting object surface G due to the inclination angle of the body frame 52. In such a case, the object of preventing dust from scattering and performing suction and recover of dust with the dust collection device cannot be attained.
Some of the conventional concrete cutters are configured with a slide guide supporting the blade cover so that the blade cover can move in the up-down direction with respect to the body frame 52, thereby making it possible to maintain the lower edge of the blade cover parallel to the cutting object surface G at all times, even when the tilting angle of the body frame 52 is changed. However, the durability problem arising in this case is that structural components (pivotal fitting section or link mechanism) can be easily damaged by vibrations occurring during the cutting operation or the like. Another problem is that the structural components should be periodically lubricated, but the dust can easily adhere to the lubricant and the maintenance becomes difficult.